To evaluate the effectiveness of both Zantac 75 and prescription strength dose Zantac in children 4 to 11 years of age. The study will provide a more rational basis for dosing in this age group. Subjects will be randomized to therapy in a 2:1 ratio of active to placebo with Zantac 75 placebo. Pharmacokinetic samples are obtained, and gastric pH is measured for six hours post dose. All subjects are then given prescription strength Zantac, and gastric pH is measured for 12 hours post dose.